The greatest champions outside of lane to counter 殇之木乃伊 include 圣枪游侠, 残月之肃, and 皮城女警. These picks are all good at countering 殇之木乃伊 with decent win rates over 57%. Even if these 殇之木乃伊 counter picks are not picked opposite your position, it's not smart to take him into one of these matchups. They will very likely win against 殇之木乃伊.
Conversely, if the enemy team choses either 大发明家 or 虚空行者, you should strongly consider choosing him, as he easily destroys these champions with win rates over 55% against both ofthem.